Non-contact vibration control system employing an active eddy current damper

Abstract

When a conductive material is subjected to a time-changing magnetic field, eddy currents are formed in the conductor. These currents circulate inside the conductor such that a magnetic field is formed. This eddy current field then interacts with the applied field resulting in a dynamic force between the conductor and the magnetic source. The force can be considered dynamic because as the eddy currents circulate inside the conductor they are dissipated by the internal resistance of the conductor. Therefore, if a continuously changing field is not applied to the conductor the force will disappear. However, the eddy current forces can be utilized to form an actuator by applying a time-changing current to an electromagnet that is in close proximity to a conductive material. This actuation method is easy to incorporate into the system and allows significant forces to be applied without every coming into contact with the structure. In this manuscript, the authors develop the concept and show that it can be accurately modeled and effectively used to control the vibration of a structure. The active eddy current actuator has not been previously demonstrated and therefore this article will present the first use of the system for providing transverse vibration suppression. Furthermore, the constraints necessary to design an active control filter will be presented. This vibration control system will use a velocity feedback filter to actively modify the current applied to the coil. Using this system, experiments are performed on a cantilever beam showing the system can effectively suppress each of the first five modes of vibration by upwards of 20 dB, demonstrating the actuator has an increased bandwidth over previously used eddy current methods.